How do I tell if my baby is allergic to one food or a whole food group?

I understand this question, and I want to give you a clear framework.

Distinguishing between an allergy to one food versus an entire food group cannot be done with certainty through home observation alone. However, these clues can help shape the clinical picture:

• Single food allergy: The reaction repeats in the same way every time that food is given; other similar foods don't cause problems. For example, if there's a reaction only to cow's milk, goat's milk or sheep's milk usually (but not always) won't trigger it, though plant-based alternatives like almond milk may be fine.

• Food group allergy: The reaction is triggered by multiple members of that group. The most common examples are:
• Legume allergy: Not just peanuts, but also chickpeas, lentils, peas.
• Milk protein allergy: Cow's milk, goat's milk, sheep's milk — in other words, all mammal milks.
• Tree nut allergy: Almonds, walnuts, hazelnuts, cashews and other nuts.

How to clarify this clinically: A skin prick test and/or specific IgE blood test performed by a pediatric allergist. These tests show which foods your child is sensitive to, but don't diagnose on their own — the gold standard is an oral food challenge supervised by a doctor.

What absolutely should not be done at home: Trying other foods from a group that caused a reaction. For example, if milk triggered a reaction, trying goat's milk at home carries serious anaphylaxis risk.

In short: keep a record of reaction symptoms and which foods triggered them, then see a pediatric allergist. Without testing, the question of "food group allergy or single food" remains unanswered.